Even if all devices are perfectly in sync at (and around) the trigger instant, each device has its internal quartz, its own PLL that generates the sampling clock. That also means that each device has its own clock deviation. While this deviation is typically below 5%, the problem is that it's totally random, and the farther you get from the trigger instant, the less signal edges are correctly aligned between different devices.

...And don't get me started on all the mistakes I've made. Some of you may have been frustrated by software not being updated or bugs not being fixed, and trust me, I was as frustrated as you, if not more. But things are not that easy. Even a very small company is a rather big ship, and steering it to another direction is not always something you can do as quickly as you'd hope. Trust me. But again: I learnt. I learnt big time.